The physics of fluctuations in heavy ion collisions is discussed and a few examples for actual measurements are presented.

In this contribution we will discuss the production of low mass dileptons in SPS-energy heavy ion collisions. We briefly review the current theoretical situation before we turn to the analysis of the recent data for Pb+Au. We also will discuss the role of baryons as a source for dileptons.

The physics of event by event fluctuations in heavy ion collisions is discussed. It is argued that fluctuations are indeed a new tool to investigate the properties of the matter created in these conditions. An example is given to show how charge fluctuations can be utilized to detect the presence of a quark gluon plasma. It is indicated that the measurement of momentum fluctuations can give an idea about the heat capacity of the systems.

This contribution is an attempt to assess what can be learned from the remarkable success of the statistical model in describing ratios of particle abundances in ultra-relativistic heavy ion collisions. © 2003 Elsevier Science B.V. All rights reserved.

In this contribution, we will discuss how the study of various fluctuation observables may be used to explore the phase diagram of the strong interaction. We will briefly summarize the present study of experimental and theoretical research in this area. We will then discuss various corrections and issues which need to be understood and applied for a meaningful comparison of experimental measurements with theoretical predictions.

We discuss the physics underlying event-by-event fluctuations in relativistic heavy ion collisions. We will argue that the fluctuations of the ratio of positively over negatively charged particles may serve as a unique signature for the Quark Gluon Plasma.

We report on recent progress concerning the theoretical description of event-by-event fluctuations in heavy-ion collisions. Specifically, we discuss a new Cooper–Frye particlization routine — the subensemble sampler — which is designed to incorporate effects of global conservation laws, thermal smearing and resonance decays on fluctuation measurements in various rapidity acceptances. First applications of the method to heavy-ion collisions at the LHC energies are presented, and further necessary steps to analyze fluctuations from the RHIC beam energy scan are outlined.